This invention relates to a picture signal recording device employed for recording color video signals and, more particularly, to a picture signal recording device which may be employed with a video tape recorder adapted for recording chroma signals after conversion which have been converted into low-frequency signals.
In video tape recorders for household use, it is customary to translate chroma components contained in the picture signals into corresponding low-frequency signals, and to record the chroma signals, as converted into the corresponding low-frequency signals, simultaneously with frequency modulated luminance signals. The chroma signals are shifted to a frequency range of from 600 to 750 kHz during conversion into low-frequency signals, and the converted chroma signals have a narrow bandwidth on the order of several hundreds of kilohertz. The converted chroma signals having the narrow bandwidth are recorded simultaneously with frequency-modulated luminance signals. Thus the picture signals may be recorded efficiently on the video tape.
With the above-described picture signal recording device in which the converted chroma signals having the narrow bandwidth are recorded simultaneously with the frequency-modulated luminance signals, since the converted chroma signals are of the narrow frequency range on the order of several hundreds of kilohertz, the chroma signal components in playback signals are less satisfactory than the luminance signal components. That is, the picture quality is lowered due to imbalances of the frequency scale. In revising the standards for VTRs for household use, emphasis has actually been placed on increasing the frequency range of the luminance signals. However, for further improving the picture quality, it is thought to be necessary to improve the characteristics of the chroma signals, such as by increasing the frequency range of the converted chroma signals.
To this end, attempts have been made in sub-sampling or sub-Nyquist sampling the chroma signals for increasing the substantive frequency range of the chroma signals without significantly changing the recording frequency range on the recording medium, such as a video tape. The sub-sampling is a sampling which is performed with an offset along the time scale, such as field or frame offsetting, or with an offset on a two-dimensional plane, such as line offsetting.
Meanwhile, if the sub-sampling is to be performed with an offset along the time scale, such as field or frame offsetting, the picture quality for a moving picture is deteriorated due to the motion along the time scale, although there is no deterioration in the picture quality for a still picture. Consequently, it is thought to be necessary to detect the motion of the picture and to perform adaptive control of the amount of sub-sampling with an offset along the time scale which depends on the quantity of detected motion.
If, however, quantity of the detected motion changes abruptly, the processing for the moving picture abruptly to change to processing for the still picture or vice versa, thus leading to edge flicker or similar defects.